The present invention generally relates to an X-ray diagnosis apparatus, and more particularly to an improvement of an arm for holding an X-ray generator and an X-ray detector.
This application is based on Japanese Patent Application No. 10-295526, filed Oct. 16, 1998, the entire content of which is incorporated herein by reference.
An example of the X-ray diagnosis apparatus is an X-ray diagnosis apparatus for a circulatory system. In this example, an X-ray generator and an X-ray detector are fixed to both ends of the arm so as to face each other. In general, there are two shapes of the arm, i.e. C-shape and U-shape. The C-shaped arm is now widely used in view of the efficiency of 3D positioning.
FIG. 1 shows a conventional circulatory-system X-ray diagnosis apparatus using the C-shaped arm. The C-shaped arm 103 is slidably held by a holder 102. The holder 102 is held to a support column 101 so as to be rotatable about a major axis (axis A1 in FIG. 1). The support column 101 is attached to a ceiling 100 or the floor so as to be rotatable about a support column axis (axis A2 in FIG. 1). Although not shown, a vertical drive mechanism may be provided on the ceiling 101. In the case of a ceiling-pending type apparatus, a rail is provided on the ceiling so that the apparatus may be movable in one or two directions.
The X-ray detector 105 includes an image intensifier (I.I.). The X-ray detector 105 converts X-ray information, which has passed through an object, to optical information and converges the optical information through an optical lens. The converged information is taken into a TV camera for image display. The X-ray detector 105 can be vertically moved by a drive mechanism (in directions toward and away from the X-ray generator 104).
The X-ray detector 105 (including the I.I., optical system, TV camera, etc.) and X-ray generator 104 are fixed to both ends of the C-shaped arm 103 so as to face each other. A rail (not shown) is provided on a rear surface or a side surface of the C-shaped arm 103. Rolls (not shown) provided on the holder 102 clamp the rail, whereby the C-shaped arm 103 is slidably held.
Because of the structure of the C-shaped arm 103, the range of angles over which the C-shaped arm 103 can slide is limited (180.degree.). On the other hand, with development and diversification of operation techniques, there is a demand for observation of finer vascular images with no overlapping with non-related blood vessels. Specifically, there is a demand for an increase in the slide angle of the C-shaped arm, which will permit image acquisition at greater angles.
To meet the demand, there is an idea that the C-shaped arm 103 is extended to increase the slide stroke. If the C-shaped arm 103 is extended, however, the end portions of the C-shaped arm 103 may physically interfere with the object, depending on the direction of access to the object, in particular, when the head portion of the object is accessed by the C-shaped arm 103. Consequently, the slide stroke may decrease, contrary to the expected result.
On the other hand, there is an idea that images are acquired while the C-shaped arm is rotated about the major axis and the projection images are three-dimensionally reconstructed to obtain a 3D image. This idea is based on the fact that the slide stroke of the C-shaped arm is limited, as stated above, and there is difficulty in acquiring all image information necessary for 3D reconstruction. When the image acquisition is effected based on the major axis rotation, there is no choice but to access the head portion of the object in order to avoid interference between the C-shaped arm and the head of the object. Therefore, the region of application of the apparatus is restricted.
Furthermore, there is an idea that the C-shaped arm is rotated around the object to obtain tomographic images. In this case, however, the angle of X-ray detection plane to the object varies and non-linear conversion needs to be performed according to the rotation angle after image acquisition. There arise such problems as degradation in image quality and an increase in time needed up to image display.
In the meantime, there is known a circulatory-system X-ray diagnosis apparatus wherein the arm is formed in a ring shape, like the X-ray computer tomography apparatus, so as to obtain a 3D-reconstructed image, the X-ray generator and X-ray detector are disposed on the arm so as to face each other, and the ring-shaped arm is made rotatable so as to perform volume scan. This apparatus can rotate in a sliding manner over 360.degree.0 and can acquire a 3D image by 3D reconstruction. However, the ring-shaped arm has no such opening as in the C-shaped arm, and the access to the object is very difficult.
The above drawbacks are present not only in the circulatory-system X-ray diagnosis apparatus but in other X-ray diagnosis apparatuses.